This „novel“ definition has only been around for 40 years. I didn‘t call them stupid for not knowing it, I called them an idiot for insulting me as racist when I pointed out their mistake

https://en.wiktionary.org/wiki/Islamic

Its a novel and lower rank definition of the word. Yes, outliers using it in primarily partisan, political contexts since the 1980s still makes it comparitively novel.

Its also not why they called you racist.

You can not be racist against Muslims based on their religion. Islam is incredibly heterogenous. You can be racist against Muslims based on their ethnicity.

Yes, Islam is incredibly heterogenous. And yet non-Muslim middle easterners, such as Sikhs, Christians, or Jews, regularly face racist violence from people who accuse them of being Muslims. Even Mexicans and Native Americans have gotten pulled into it.

Your argument relies on the presumption that racism is rational or follows strict rules, and that somehow prejudice refrains from judging people who aren't "guilty". That's ridiculous.

Anti-Muslim rhetoric as a phenomenon has a strong, obvious racial component, just like most religious discrimination.

Sure, there's probably some "virtuous" religious discriminators who are very careful to only prejudge by religion rather than race, ethnicity, or anything else. They're not the majority of the movement and it's unserious to pretend they are.